Silver halide photographic materials which are more easy to use and have higher sensitivity have recently been prevailing by the progress of techniques of improving image quality. Above all, in the field of widely used photographic materials for photographing, the speed of sensitivity has progressed from an ISO sensitivity of 100 to ISO 400. There are the development and progress of the so-called DIR couplers, that is, couplers which imagewise release development inhibitors, in the technical background which makes possible such speedup of sensitivity. DIR couplers can extremely improve color reproducibility and sharpness respectively by revealing the interlayer effect and the edge effect. On the other hand, DIR couplers bring about undesired influences such as the reduction of gamma (low contrast), the reduction of sensitivity, the reduction of color density and the like. A technique which uses a coupler which releases imagewise an electron transfer agent in combination with a DIR coupler for compensating for these drawbacks is proposed in U.S. Pat. No. 4,859,578 and European Patent Publication 347,849. However, the releasing speed of the electron transfer agent of any of the couplers disclosed in these patents is slow, therefore, this technique is not satisfactory for the intended object. Couplers having heightened releasing speeds of electron transfer agents are later proposed in U.S. Pat. No. 5,104,780 and JP-A-3-167550 and JP-A-3-209240 (the term "JP-A" as used herein means a "published unexamined Japanese patent application"), but they do not yet attain a sufficient level.
As are required for all recording materials, a silver salt photographic material is also required to be led to the final form by a rapid processing. The speed-up of the development processing stage in which various chemical reactions proceed has been one of the important subjects of the development and research in the case of a silver salt photographic material. A technique of heightening the development speed by releasing an electron transfer agent at processing time is disclosed in U.S. Pat. Nos. 4,554,243 and 5,019,492. This aims is to attain the storage stability of a photographic material and the speed-up of the development process at the same time by incorporating an electron transfer agent having an active moiety protected by a blocking group into the photographic material and removing the blocking group at development processing time. However, this technique has a drawback that the development proceeds in a certain degree in unexposed areas (unexposed areas are fogged largely), although the incorporation of the electron transfer agent into the photographic material certainly increases the development speed. This is because the electron transfer agent is released uniformly irrespective of the exposed and unexposed areas. Accordingly, the development of a technique of imagewise releasing an electron transfer agent has been required to avoid the above drawback. Therefore, various methods of incorporating a coupler compound having a coupling position bonded with an electron transfer agent into a photographic material have been investigated. Some examples of these couplers are disclosed in U.S. Pat. No. 4,546,073, Research Disclosure, No. 25758 and JP-A-61-113060, but any of these compounds has not sufficient coupling activity and the release speed of the electron transfer agent is small, therefore, the sufficient accelerating effect of the development speed has not yet been obtained.